1. Field of the Invention
The present invention relates to a thermostat that changes a passage of a coolant depending on the temperature of the coolant and actively controls the coolant temperature to prevent the overheating thereof.
2. Description of Related Art
A thermostat for a vehicle is disposed between an engine and a radiator and is opened/closed by the temperature variation of coolant to adjust the flow rate of the coolant, and therefore the temperature of the coolant is controlled in a predetermined range.
A mechanical thermostat expands wax depending on the temperature of the coolant, and the expanding force of the wax makes a piston move the valve of the thermostat.
The mechanical thermostat is operated in a predetermined opening/closing temperature of the coolant to open/close the valve only in a predetermined temperature condition, and therefore the mechanical thermostat does not actively move against changes of the driving circumstances of the vehicle.
Accordingly, an electrical thermostat has been introduced to complements the drawback of the mechanical thermostat, and the electrical thermostat is operated to sustain the coolant temperature in an optimized range.
The electrical thermostat actively controls the coolant temperature of the engine according to the driving circumstances such as the load level of the vehicle to sustain the optimized coolant temperature, and the electrical thermostat can improve fuel consumption efficiency and reduce exhaust gas.
Meanwhile, three coolant passages are formed in a thermostat as an example. A first passage is connected to a radiator, a second passage is connected to a coolant outlet of the engine, and a third passage is connected to a coolant inlet of the engine. Here, the coolant pump can be disposed between the third passage and the coolant inlet.
In this case, the first valve of the thermostat opens/closes the first passage, the second valve opens/closes the second passage, and the third passage is opened. Further, a guide can be disposed to guide the movement of the first and second valve.
Meanwhile, a first valve is operated by a drive portion to open/close the first passage, a sealing member is disposed between the first valve and the drive portion to form the sealing structure between them, but the sealing member cannot perform its function by anti-freezing solution of coolant or foreign material.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.